The present invention relates to an antenna system which includes at least two antennas for frequencies up to an ultrahigh frequency range. The antennas are arranged on a non-conductive sheet such as a window pane framed in a metal body of a motor vehicle. Each antenna has at least one antenna conductor secured on the non-conductive sheet, a connection point on the antenna conductor, and a four-terminal network having two input and two output terminals.
Antenna systems of this kind are known, for example from the German application P 37 19 692.8. Such known multiple antenna arrangements on a single window pane of a motor vehicle provide a cost effective antenna diversity system for the ultrahigh frequency range or for the television frequency range, for example. The antenna diversity systems of this type require at least two antennas and provide a distinct improvement in the reception.
From the point of view of installation into a motor vehicle, such antenna systems are preferably designed so as to permit their integration into the body of a motor vehicle. This requirement is best met by so-called window pane antennas. Preferably, either the windshield pane or the rear window pane of a motor vehicle, due to their relatively large area are used for this purpose.
Prior art antenna arrangements, for example, in FIG. 1 of the German publication P 37 19 692.8, when used in connection with motor vehicles, have the special disadvantage that they require wire bridges or conductor bridges between a connection point on a conductor on the window pane and networks mounted on the body of a motor vehicle. Each of the networks extending on the vehicle body requires an attachment point on the electrically conductive body of the vehicle which frequently is identical with the present grounding point for high frequencies. From the point of view of a manufacturer of motor vehicles, this known arrangement of antennas has the considerable disadvantage of requiring a large number of conductor bridges from the pane to the vehicle body and a large number of individual components which in the course of production of the vehicle must be installed and connected. The assembly of the requisite grounding and, evidently, of the requisite mounting points in practice is also difficult for the vehicle manufacturer inasmuch as grounding and attachment points among other requirements, have to be readily accessible during the installation process and also for a possible exchange of defective components and, at the same time, they must be covered by screens under which the aforementioned extended networks take place.
Moreover, since the extended networks are distributed around the window pane of the motor vehicle, a complicated cable network for the antenna arrangement is a further disadvantage, because the output signals from the respective extended networks must be fed via a separate line to a diversity processor. With the increasing number of separate components needed for the antenna system, the cost of maintenance and storage of such component parts also increases, thus contributing to the disadvantages of prior art solutions.